Apparatus for injection molding thermosetting compounds



W. R. TUCKER APPARATUS FH lNJECTION MOLDING THERMOSETTING COMPOUNDS Filed Deo. 1a, 1969 lmvtm'oa WARREN RUCKER 5 Sheets-Shee l Filed Deo. 1e, '1939 n y om. d.: 3. 'ab

APPARATUS FOR INJECTION MOLDING THERMOSETTING COMPOUNDS May 4, 1943.

May 4, 1943.

APPARATUS FOR INJECTION MOLDING THERMOSETTING COMPOUNDS W. R. TUCKER `Filed Deo. 18,1939 3 sheets-sheet s .1 Y, WT.. N..

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Patented May 4, 1943 APPARATUS FOR INJECTION MOLDING THERMOSETTING CORIPOUNDS Warren R. Tucker, Dayton, Ohio, assigner to The Hydraulic Development Corp. Inc., Wilmington, Del., a corporation of Delaware Application December 18, 1939,v Serial No. 309,798

8 Claims.

This invention relates to apparatus for injec tion molding of thermosetting compounds such as for example the thermosetting phenol formaldehyde resins, urea formaldehyde resins, phenol modified urea resins, urea modified phenolic resins, and other thermosetting resinous compounds and mixtures.

It is an object oi the present invention to devise an apparatus which makes possible the injection molding of a thermosetting material by allowing the plastic thermosetting material to be heated to the fluent injectable form in an injection cylinder without being converted in the injection cylinder to the nonplastic state; the thermosetting material thus rendered iluent is injected into the mold cavity while in this uent form and is subsequently hardened in the mold cavity; the material being heated in 'the injection cylinder is prevented from appreciably losing its plasticity and from undergoing to any appreciable extent the irreversible reaction which characterizes the setting of thermosetting materials.

It is another object of the present invention to carry out the processes outlined above by preventing the escape of gases from the thermosetting plastic as it is being heated in the injection cylinder; in this way, the plastic may be heated sumciently to soften it and to render it inject` able and it will stay in this plastic condition until the gas is liberated; in a preferred form, the escape of gas is substantially completely prevented while the material is in the injection cylinder and after it has been injected into the mold cavity the gas which Atends to be given oi is allowed to freely escape and thus the thermosetting reaction may be carried Ito completion in the mold cavity; the present invention is based upon the factthat when thermosetting molding materials are heated. to cause them to set an irreversible reaction takes place-which is chemical in nature and causes the liberation of certain gases, and that if these gases are prevented from escaping, the plastic thermosetting material will soften and remain fluent until the gas is liberated, even though heated to a point which would cause initiation oi the thermosetting reaction were the material unconiined and the gases free to escape.

It is another object of the present invention to devise apparatus for the carrying out of the process as outlined above, wherein the plastic in plastic itself and prevents the liberation of more gas. therefrom, and wherein the material thus rendered uent is injected into the mold cavity while maintaining conned that portion thereof which remains in the injection cylinder.

Another object is to devise apparatus of the type just outlined wherein an extremely close fit is provided between the injection plunger and theinjection cylinder, so as to positively prevent the escape of gases between the injection plunger and the wall of the injection cylinder; inone form of apparatus, this result has been attained by making the injection plunger slightly "larger in diameter than the receiving bore therefor in the injection cylinder, and by heating the injection cylinder in the usual manner, while cooling the injection plunger, so as to reduce its diameter to the point where it will just enter the injection i' cylinder; in this way, an extremely small clear- W ance is provided between the plunger and cylinder wall and the escape oi gases ,therebetween is eliminated whereby t'is possible to allow'a y relatively high gas pressure to be builtupiby the thermosetting material being heated in the heating chamber; another advantage of'cooling the injection plunger is that the flow oi' plastic 4materiai by the injection plunger which might cause galling of the sliding parts is prevented since the plastic immediately ahead of the injection plunger is maintained in'its granular noniluent form. l l

Another object is to provide apparatus of the foregoing type wherein the injection nozzle is valved and wherein suitable means is provided for actuating the valve at the time of injection so as to allow injection of the fluent `thermosetting material from the injection cylinder into the mold cavity; in a preferred form, this valve-is actuated at the time when the mold parts vhave been clamped together. k

Another object is to provide apparatus for carrying out conveniently the process outlined above, whereby the operator may conveniently and rapidly carry out this process; in a preferred 'f form substantially all of the operations of the machine are automatic and it is necessary for the operator to manipulate only the mold clamping switch and the mold unclamping switch.

Numerous other objects of the present invention will more fully appear from the vfollowing detailed description of l modes of carrying the same into practice and of kone form of apparatus which has been found particularly advantageous for the carrying out of this process.

In the accompanying drawings;

Fig. 1 is a. diagrammatic view of an apparatus Fig. 4 is a longitudinal sectional view through the injection cylinder with the rear portion of the injection cylinder proper in elevation.

Fig. 5 is a detailed longitudinal section showing' a modification; in this modification a valve member is pushed rearwardly by the action/of clamping the mold halves together and to the injection cylinder.

Fig. 6 is a section taken on the line 6-6 of Fig. 5, looking in the direction of the arrows.

GENERAL Priocsnrmr:

In accordance with the process of the present invention, a thermosetting molding material is' heated in an injection cylinderrto the point of uency while preventingthe liberation of gases therefrom, and the iiuent material thus obtained is injected into the mold cavity where the material is subjected to heat to cause it to harden into the ilnal shape and wherein the free escape of gases is'permitted. The thermosetting reaction of the thermosetting materials. is a `chemical reaction, taking place under the' application of heat at 'or above a certain critical temperature, and causes the liberation of certain gases from the material as the reaction proceeds. If

these gases are prevented from escaping from` the material by suitable means, the plastic material will soften andwill remain fluent until the gas is liberated. Thus, by bringing the plastic material up to a. temperature at or slightly above the critical temperature mentioned above while preventing the escape of gas therefrom, softening and ilow of the material will take place without further aiding in the prevention of the liberation the setting reaction occurring. 'I'hen by injectj inga portion of the material into the die 'and allowing the gas to escape from the material after it leaves the heating chamber and while the piece is in the die, injection molding of thermo-setting materials may be accomplished.. The die will be held at a temperature at or above the critical settingtemperature mentioned above and previerabiy well above this temperature in order to assist in the driving en of the gas in the mold. Conventional dies may be employed, it being understood that such dies allow the free venting of the molded article, dies being provided with venting passageways in order to allow the escape of the air in the die as the material being molded is injected into the mold. In many cases, the dies need not'have special venting passageways lbecause it is frequently impossible or impracticable 'to make an absolutely tight fitting die assembly. j A

Once during each cycle, additional plastic is desirably added to the heating chamber where vit is progressively heated to the softening point.. i The general construction of a machine for carrying out the foregoing process will be similar to that of the present injection molding machine used for injection molding of thermoplastic molding materials. The injection plunger will fit very closely in order to prevent gas escaping V`from the heating chamber.

between it and the injection cylinder. The injection nozzle is provided with a valve which closes oil! and opens the injection passageway leading Means is provided for opening this valve at the time when injection' is desired. Thus, the escape of gases from thel heating chamber is prevented. The injection plunger will be at substantially all times held under pressure against the material in the heat ing chamber and consequently the material therein will substantially iill the heating chamber thus provided and the preliminary slight escape oi gases from the material to this closed chamber will develop a very high gaseous pressure in the heating chamber. It will be understood that the injection plunger will be brought forward and held against the plastic in the heating chamber under high pressure, this feature of gases from the plastic material. Then when it is desired to illl the mold cavity, the mold halves will be closed'whereupon the valve in the injection passageway or nozzle will be opened,

whereupon the injection plunger will move forward under this same pressure, causing injection to take place. After the mold cavity is fllled,.it

is preferable to hold the injection plunger for- Y ward underthe same pressure untilthe molded article has cured sufliciently to hold its shape,

-whereupon the nozzle valve will be closed, thel injection plunger retracted for a new charge and brought quickly forward so as to prevent as far as possiblev escape of 'gases from the heating chamber. As lthe injection plunger comes forward, it will compress the new charge into the heating chamber. Meanwhile, the mold halves f have been unclamped, the molded article ref moved and the apparatus is now ready for a repetition of the cycle.

' Apparatus employed The process of the present invention can per- I haps best be understood by .a description of the apparatus shown in the drawings, wherein the injection cylinder or heating chamber is designated generally as l and is adapted to have the injection plunger 2 reciprocated in its bore. The

injection lcylinder l is flxedly mounted in anyv suitable'mannervupon the strain rods 3 which extend longitudinally of the machine.l The cylinder I has the injection nozzle 4 against which the mold half 5, flxedly carried upon the bolster l which is slidable yrelative to strain rods 3, is adapted to be moved into injecting relationship. Cooperating with mold half 5 to form the mold cavity is the other mold half 1 which is fixedly carried by a bolster 8 which is likewise slidably mounted upon the strain-rods 3 in any suitable mannerandwhich is adapted to be moved by the clamping ram 9 which is integral with a hydraulic piston I0 reciprocable within a hydrauliccylinder H, the cylinder Il and the piston I0 forming a double-acting hydraulic motor for actuation of the mold clamping ram so as to unclamp and is sumcient to cause tight engagement therebetween but insufficient to cause injury to or deformation of the nozzle 4. It will be understood that the cushioning cylinders I3v are xedly mountedwith respect to the strain rods 3. rThe cushioning cylinders I3 and cushioning rams'I2 are shown in Fig. 1, but are not seen in Fig. 2'

because they are mounted in the same horizontal plane as the injection cylinder I and therefore one of them is concealed 'behndthe apparatus shown in Fig. 2, while the other is forwardly,

thereof and is therefore not seen inthe medial section represented by Fig. 2.

The injection cylinder I is of substantially a conventional type, having a heat insulating jacket I4 of rock Wool surrounding the injection cylin-l der proper designated as I5. Between jacket I 4 and cylinder I 5 are a pair of spirally wound electrical heating elements I6, these heating lelements being alternately disposed around the heating cylinder I5. A thermostat I 1 is provided inwardly of the jacket I4 and this ytherinostatlis adapted by suitable connections to control the f application of electrical energy to one or bothof the heating elements I6 so as to maintain the desired temperature in the heating chamber. 'I'he heating cylinder is provided with xthe conventional torpedo I8 which is screwed into the forward end of cylinder I5 and which forms the annuiar heating space I3 connected to the injection passageway by the forwardly converging -passageways 2| in the` torpedo I8. When the linjection plunger 2 is received within the cylindrical bore 22 provided therefor in the cylinder I5, there is formed a cylindrical space 2 3 ahead of theinjection plunger, which space is adapted' to be varied in size bythe movement of injection Theinjection -nozzle 4 is provided with a valve for opening and closing'the injection passagewayl 20, this valve being shown as taking the form cfa tapered valve member 24 which has a transverse bore 25 therethrough whereby when the valve member 24 is rotated to a position at right angles to that shown in Fig. 4, the bore 25 which is ofthe same diameter as vpassageway 20 allows free passage of. the fluent plastic material out of For actuating the valve 24, a hydraulic motory Y 23 is provided, this hydraulic motor having a pisf .i

ton which is operatively connected tothe valve member 24 and which is normally spring-pressed 1 in such a direction as to maintainthe valve 24 closed. When the hydraulic motor 28 is supplied with liquid under pressure, its piston is actuated in such direction as to open the valve 24 and to allow injection to take place.

Charging mechanism Disposed rearwardly of the injection cylinder I is suitable supporting mechanism which supports ehargingmechanism for charging the heating chamber. l 'I'he injection cylinder I mounted ahead of a member 29 (Fig. 2), being separated therefrom by the layer of heat insulation 30, member k29 being flxedly carried by a supporting member 3| which is xedly attached in any suitable manner to thestrain rods 3 and thus supports the injection cylinder Iagainst movement with respect to rods 3. The supporting member 3l also supports above it a hopper 32 whichgis adapted .to receive the cold granular plastic and which is provided with a. screw conveyor 33 for conveying the material into a feed elbow 34', the lower end ofwhichis tightly received in the upper portion of member 29. Thus, the screw conveyor 33 is adapted to supply under continuously exerted pressure the granular plastic material above the injection plunger 2 in the member 29 so that when the injection plunger is retracted. this granular material is forced downwardly ahead of it and when the linjection plunger is moved forwardly, the charge thus placed ahead lof it is compelled to move into the space 23 which constitutes the rear yportieri of the heating chamber. In practice, it is desirable v to retract the injection plunger 2 until its forward end is substantially in alignment with the rear wall 35 of the feed pocket in the member '29 whereby a maximum charge is moved into the injection cylinder with each stroke of the plunger -2. For inspecting the charging'or for removing plastic from the feed elbow A34, al normally n tightly closed door 36 feed elbow34. v A

The heat insulation 30 tends to prevent the transfer of heat 'from the injection cylinder I to the member'ZS and to the granular plastic above the injection plunger 2 and in the feed el-l bow 34 However to further prevent softening of the granular plastic before it' has been transferred intothe injectiony cylinder I,y a cooling maybe provided in the passageway 31 is provided in the member 23.

This passageway 31 may be annular so as to para tially encircle injection plunger 2 and 'is supsuitable mannerwith 4a cooling plied in any Means for insuring .aas tight fit of injection plunger In order to attaina fit between `the injection plunger 2 and the bore 22 in the injection cylinder I5 which will prevent the escape of gases even though an extremely high gaseous pressure is developed in the heating chamber, the plunger-v 2 is made slightly larger than .the bore 22 when the plunger, 2 and the'injection cylinder I5 are at the same temperature, sayroom temperature. l For example,`the plunger may be vfrom001- .to .0005 in. larger thanbore 22.` The injection vplunger 2 is cooled so as to reduce its size to just under that of bore 22. It rwill be understood that since the injection cylinder I5 is heated, lts bore 22 will expand somewhatand by cooling the injection plunger an extremely close n t which is gas tight butwhich allows sliding of the injection plunger 2 in the bore 22 is obtained. To maintain the injection.. plunger 2 at this relatively reduced size, it is providedQwith the cooling passageway 38 which extends up to a point close to the forward endof the injection plunger and which is supplied with cooling liquid by means of.fiexible conduit 39 (Fig. 3), and from which the cooling liquid is discharged'` by means of :dexible conduit 40. l

may be injection plunger 2 is that the granular plastic immediately ahead of it is prevented from becoming fluent and flowing around the injection plunger. In addition', the granular plastic above the injection plunger 2 and in thefeed elbow 34 is prevented from becoming fluent, which might interfere with the cliargingioperation.l

In addition to the foregoing provisions for obtaining, a close nt between the plunger 2 and the bore of the injection cylinder, it is desirable Vto malte the surfaces of the injection plunger 2 and of the bore .22 super-nnished. In some cases,

Another desirable advantage of cooling the' 55 being rotated to either of its two positions by y the reversible three-phase electric motor 5l. The

inlet conduit 62 for valve 50 is supplied with low pressure liquid at all times by reason of its connection with conduit 46. The inlet conduit 62 is adapted to be connected by the rotary valve 50 either to the conduit 63 which leads to the top of valve 56 for shifting the valve member therein itmay be desirable to make these parts or surf faces of extremely hard material, for example by making them of 'high chrome steel or chromiumV plating them. These expedients further aid in the preventing of galling and in the maintenance of-a` gas tight but relatively easily slidable llt therebetween. f

Hydraulic circuit For operating the several hydraulic devices. high pressure liquid is supplied by a high pressure pump 4I and low pressure liquid at relatively large volume is supplied by a low pressure pump'42, these pumpsl being drivenby an electrical motor 4l and drawing liquid from a tank 44.` The output of-high pressure pump 4| is delivered into a conduit 45. The low Vpressure pump 42- discharges into a conduit 45. A conduit 41 connects conduits' 45 and 4l. A check valve 4P is located in connecting conduit 41 and serves to `allow liquid to pass from conduit toconduit 41 but to prevent the reverse now of liquid. This check valve 4l closes when the pressure in line 45 exceeds a predetermined high figure. thus preventing the low.pressure from entering conduit 41 and shifting the operation of the clampingand cushioning cylinders from the outflow from 'cushioning cylinders I3, thereby insuring that the mold halves 5 and 1 are clamped securely together before the mold half 5 is in intimate contact with injection nozzle 4.`

Hydraulic control of injection plungery The hydrauiic circuit is 'sc arranged that the high pressure output of pump 4I is never applied to the injection plunger 2 which is actuated by the piston u in the hydraulic' cylinder 55, and that the double-acting hydraulic motor which actuates injection plunger 2 is always operated by the low pressure outputof pump 42. In order to accome plish this, the low pressure conduit 48 is connected to a four-way valve 56 for controlling the injection plunger 2. The serviceconduit 51 connects four-way valve 5E to the forward side of piston 54 and a similar service conduit 58V connects thel The valve valve 55 to the rear sitle of piston 54. member in valve 55 is adaptedto connect either conduit 51 or conduit 58 to the inlet conduit 46 and to connect the other conduit, 51 or 58, to a return conduit 59 which leadsback to the tank 44. Y l

For actuating the valve member in valve 5S, a rotary four-way valve 60 is provided, this valve duit 14 and to thereby allow free dovmwardly and thus connecting the low pressure in pump 48 tothe righthand 'side of piston 54 so as to move the injection plunger 2 forward, or to `communication with the inlet conduit 52 to the. y

exhaust conduit 13 and thus allows discharge of the liquid from the side of valve 56 towards which the valve member therein is being actuated.

Hydraulic control of mold clamping and nozzle opening The conduit 45 leads to a four-way valve 45. the valve member of which is adapted to connect conduit 45 either to a conduit 66 leading to the right hand of clamping piston l0 or to a conduit 61 leading to the left-handl of clamping piston Il.

At'the same time, the valve member of valve 35 connectsl the conduit 66 or 61 which is not connected to the inlet conduit 45 to the return line 59 leading back to the tank 44.

In order'to actuate the valve member in valve 65,

a four-way rotary valve 68 is provided, this valve having a rotary valve member adapted to be actuated to either of its two positions by a reversible three phase electricmotor 69. Valve 64 is connected by the inlet condllltrl to the conduit 4lv and is thus supplied at all times with liquid either under high pressure from pump 4| when check valve 48 is closed, or under low pressure from pumps ,42 and 4| when check valve 48 isopen. 'Ihe valve member of valve 68 is adapted to connect Ithe inlet conduit 10 either to a conduit 1| which leads to the top of valve 65 and to thus cause the valve member in valve 65 to be shifted .downwardly so as to connect inlet conduit 45 to conduit 61 so as to cause the clamping ram 5 to move towards the injection cylinder l, clamping the mold halves together, or to a conduit 12 which leads to the bottom of valve 65 and whichis adapted to supply liquid pressure to cause the valve member in valve 65 to shift upwardly so as to connect the inlet conduit 45 to the right hand of clamping piston i0, thereby causing unclamp..

ing ofthe mold halves.

Rotary valve 68 is provided with an exhaust conduit 14 which connects with the exhaust conduit 13. Rotary valve 58 is likewise adapted to connect the conduit 1I or 'l2 which is not connected to the inlet conduit 10 to this exhaust conmovement of the valve member in valve 65.

Conduit 15 is providedibetween conduit 58 and the clamping and unclamping cylinder Il, this conduit 15 extending into communication with the space at the right-handof piston I0 at a disstance from the inlet of conduit 66 towards the left therefrom. This conduit 15 'has a check valve 18 which allows liquid to pass outwardly through conduit 15 but prevents its reverse now. 'I'he purpose of conduit 15 and check valve 16 is Velectrically as follows.

Hydraulic actuation of Ainjection valve:

As indicated Vdiagrarnrnaticallyy in Fig; .1, the hydraulic valveactuating motor 281s adapted to be placed into communicationpwiththe clamping conduit 81' through a conduit 11by means.

. of an. admissionV valve 18, the spring-pressed valve member ofv which is adapted to be'moved upwardly of Fig; 1 when the: pressure inxconduit' 8 1 exceeds a predetermined. amount so as. to uncover the inlet of conduit 11 to admission valve 18 to thereby allow the fluldpressure. to be com- 82.; VThus-. normally are circuit is: established throughv the; coil 85,causing thearmaturedlf be'fpulled-.l'eftwardly'oi 1, causing motor` 8 to. rotatathe. rotary valvefllltozsuch directionI as to` deliver' pressure liquid to', the top. oij recipro cable; valve.- 58', thus causing` the-` liquid, pressure. inline I8 tov be. normally` applied.` to. the". rightl tion-'plunger 2j to: bev normally pushedi forwardlyv sol vasto exert-a holding pressuresupongtheimate rial' in the injection cylinden.v spr-ingr- |.8|'.at:- tached toxarmature fis` adapted to pullgitzrighta wardlywhenever the` circuit: througlrcoili 881/ is broken, therebyV breaking thefholding circuit municated through conduit 11i into g hydraulic.,

. motor 28 so as to open the injectionnvalve. 25

when. theA clamping pressure exceeds a. certain iiguredue tothe vcoming togethenof the mold halves. pressure from'hyd'raulic motor 28, a check valve conduit 18 having a check` valve 88A is provided betweenr conduits 111 and 61. Thus, as the moldhalves come together under`V the application of liquid pressurey to the left-handler piston I8, the liquid pressure increases in conduit 81, causing valve 25. to be opened by motor 28, allowingthe injection plunger' which is held forward under pressure to move forward under this same hold-- ing pressure to cause injection.k 'A fter Ainjection has taken place and the application of liquid pressure is transferred to. the right` hand of. clamping pistonA I8 so as to cause unclamping of the mold halves, the lowering of liquid .pressure in conduit. 81. causes the valve member; 'in'Y valve 18 to move undenthe action `of its spring so asto cover the inletl of conduit` 11 whereupon the motive` element in hydraulicm'otor 28 An'ioves un der. the action of its spring so as .to close injection valve 25, the discharge of liquidv fromxnotor 28 taking place through check valve 88". and conduit 18- into conduit 81 which is now connected so as to discharge into thetank M. Y Electrical circuit controlling.` injection plunger 'I'he operation of lrotary valve 882'is controlled The vmotor '8| or rotary valve 68 is connected so as to be operated in either direction from the incoming three phase line comprising wires 8|, 82y and 83, by means of an armature. adapted to be pulled inY one directionV by al solenoid coil 85.

8| is operatedlin one direction and wheninanother position, motor 6| is operated'in the reversel direction. The. solenoid. coil. 85 is adapted to; be

energizedby the closing oi'anormally open limitswitch 88 whichis arranged so as to. be actuated" bythe injection. plunger 2 when it reachesnits.

fully retracted position, one side of the switch 88 connectedby a wire 8i to anormally closed, man1- ually operableV switch 85. theother side of which is connected by a wire 86 to one contact 81 of a normally closed switch, the other contact 8 8 of Armature 84Y carries switch. arms 86, 81 .and 88. which'V are so. connected that when' in one position, the motor For allowing release of; liquid under A propriete point on the'clamping'ram1-p8; Tripestablished by the: bladell` and causing motor'- 8| to operatef in'v theA reverse: direction whereby the` valve: plunger/in valvesf" moved: upwardly' so as to connect. conduit I8; tosconduit. 81-k whereby lthe injectiomplungerfis retracted;k The purpose of-.the manuallyoperatedi-switch 8551s. `to` allow *retraction OII'the-.inJectiOnpIunger for filling the heating.l chamber: atithe` of' operationsi This switch is4 opened; manually'to.

cause the injection plungerito retract; and. whenthe operator sees thatthe. injection: plunger has retracted, he closes switch: 85, causing theinjec-Y tion" plunger to .push .its chargehforwardly into theheating' chamber; This i'arepeated: severalV times until the heating chamber. isfull'f.

In order to cause retraction-` of" the injection r plunger atv a predetermined time .afterinlection has; been completed; provision is'- madel for: auto matically retracting plungerY 2r at: a time: whichl is measured from the'ftime when-the clamping ram 8 attains a givenrn'isitiorrl ina its: clamping stroke. This meanstakes. the form.; ott theY trip' switch |82 which is adapted to. be tripped; by; a trippingmember |88 xedly'carried; at au'arap-l ping member I 83fis adapted. to trip" the switch. |82. in. ,only the. forward direction' of.. operation. of. the ram` 8.. Preferablyl the. tripping; member |88 is` adjustable longitudinally' ofi clamping; ram 8,. as Ishown, wherebyk adjustment .may be. made. in time when switch |82is tripped; .In'this'wam lswitch |821. is tripped onthe'forwardclampingy movement of ram 9 and.isgadaptedvtoiinterconnectk aV line |84r which. connectsto linev 88'@ and thus to power linel 88 andvazline' |-85 whichzcon nects toone side'ofa ltiming motor: |-.88,-..thef.other.

side of which is connected.- by a; linei |81 toathe` -une looandthueto theinceminepewernnen. As a result, whenswitch'v |82isizr'iplrfedglthetinii-V ing motor |86 is caused: torrotatey in. va .direction4 clockwisev of Figc. I. andto rotata-timing;cam'.y |28'8..

. Immediately when .tlming'cam I8 8? beginsltoz-z 11o-1v miie eenneetedfty a; une. fn te. menne m; v

while contact' |88 isf similarly connectediflziy ai vline-H2 to the linel 851. Thus afholdngicircuiti is established themomentwhenmotor l88begins 'e t0 rotate. whereby the motor um.V ist eu'ewedf torotateuntil. oneY revolution. has: been'. completed;

whereupon the timingcam-.z I tcausessopening: Y Y of? the contacts I 88-and |18', causing#rotation;off.A

the motortoceasa As.- the. timing. cam. i881. is` rotated and: after a. predetermined. period.k after'. the tripping.. of; switch |82, it: causesV openingr ofi contacts81fand 88, thereby causing degenergization: ot coil'85,

. causing reversal of motor 8|, in. turn. causing-f application ofiluidpressure to be. transferred from which. is.; connected by, aa wire.. l8rto af wi'rez-V |88-vv which is'connectzectv to the: incoming.. power." .linee handv of injection piston 84; icausi'ng'- the; viniecn-V l the top of valve 56 to the bottom thereof, causing interconnection of cnduits 46 and 51, causing retraction of theinjection-plunger 2.

.As the injection plunger 2 lattains its fullyl re- Y tractd position, it closes the normally open limit -switch 89,' thereby causing: coil 85-to be again energized and causing reversal-of motor 6|, caus- -ing the injection plunger 2 vrto move'forwardly, vthe parts'being as shown in Fig. 1. It will be understood that the timing cam |08 will have continued'to rotate 'in'the meantime and will have closed the' contacts 91 and 98 so' that the holding circuit .is'established' by switch blade 9| at theinstant when the limit switch 89 is closed.

Electrical circuit controlling clamping ram The motor 69lwhich actuates the rotary valve 68 so as toshift the valve member in the valve l .to controlmotion of the clamping ram 9, is adapted to be placed into connection with the incoming powerlinesBl, 82 and 83Y by suitable cnnecting wires adapted to'be interconnected by which'isadapted to be normally pulled'right` l ,wardly of Fig. 1 byaspring ||1 whereby rotary valve, 6811s shifted normally so as to normally Vposition the valve-member in valve 65 upwardly,

connecting pressureconduit 45 to the unclamping conduit 66 and applying liquid'pre'ssure to the right hand o1' the clamping piston l0. In 'order to pull the armature ||6 leftwardly of Fig. 1 so as to lreverse the application of liquid pressure from conduit. 69 to conduit 61, solenoid coil II8 .is`provided for *armaturev H6. This coil ||8 is :connected bya line ||'9to the power line 82 and fthe other-end of coil ||8 is connected to a wire :120, one end of which leads to a contact adapted tobe engaged by a manually operated clamping switch I2|. connected by a lead |22 V'to the incoming power line 83.*Wire also is connected to a contact z which isi adapted to Vbe engaged by a holding The othercontact of switch |2| is switch bar' |23 flxedly' mounted on the amature H6.. The other contact engaged by switch bar |23 isconnected by a wire |24 to one side-of a normally closed, manually operated unclamping switch |25, the other endl of which is connected to power line 83. Inthis way, closing of switch |2| Vmanually causes thecoil I8 to be energized, 'resulting in the shifting of the valve member in valve 65 and causing the liquid pressure from conduit 45 Vto bev applied to the left-hand of clamping piston I0, thus causing clamping ram 9 to move rightwardly, clamping the mold halves. l

As soon as switch I2| is 'actuated a holding circuit is established by switch bar |23. With the mold halves clamped, manual opening of switch breaks the holding circuit and allows the armaturer||6 to bemoved rightwardly by its vspring II1, causing the valve memberin valve 65 to assume the position of Fig;v 1 and causing A-.unclamping of the moldy halves.

OperationY .The operation of theapparatus is as follows: Whenstarting operation, the injection plunger 2 is reciprocated several times by opening manually the switch 95 several times, the switch -95 being held open each Atime until the injection plungerhas fully retracted and then being allowed toclose so as to move the injection plunger forwardly, packing the granular plastic into the heating chamber. When the heating chamber is thus iil1ed,1 this reoiprocation is ceased, the

`. switch 95'beingV closed-'and the inJection plunger 2'is now held forward under pressure from conduit 46. During this time, thefclamping ram 9 is held retracted because the vvalve 65 is in the position shown in Fig. 1, the'is'tart or clamping switch :I2| being open.

To initiate the molding operation, the clamping switch I 2| is closed manually, causing the reversal oi' motor 69 and the'V shifting of the valve member in valve 65 so as to cause the application of low pressure liquid from conduit to the left-hand of the clamping piston |10. This causes 4the clamping ram 9 to move rightwardly; bringing the mold halves toward one another. At the same time, the' same'liquidpressure is applied to the cushioning cylinders I3. n halves come together, the resistance oiered by vthe choke 52 allowsA'the cushioning rams I2 to move slowly rightwardly until the mold half 5 engages the injection nozzle -4. In the meantime, the resistance to -1low in line 61 has caused the check valve 48 to'close and caused the high pressure output of pump 4| to be applied to the lines 61 `and 49.'v 'I'his causes high clamping pressure to be exerted on the mold." As the clamping ram 9 approaches its innermost position, at which time the mold halves are closed andthe apparatus is ready for injection, the tripping member |03 carried by the ram 9 causes the trippin'gof the trip switch |02, energizing the timing'motor |06 andV causing, it to begin to rotate whilethe clamping pressure is further builtV up to a maximum. As soon as the motor |06 begins to rotate, the cam |08 causes closing of contacts |09 andV ||0, thereby establishing a holding circuit which keeps motor |06 rotating.

After clamping of the mold halves is complete, theincreasein pressure in the line 61 above the high pressure therein causes opening of the admission valve 18, allowing the liquid under this extremely high pressure to Vbe admitted to the nozzle valve operating motor 26, causing the nozzle valve 25 to be opened; As soon as the valve 25 opens, the injection plunger 2 which was already held forward under pressure, moves for- ;ward causing injection o1' the uent material from th heating chamber into the mold.

Meanwhile the timing cam |08 has continued to rotate and after a predetermined timesuillcient to allow complete lling of the mold and suillcient holding of pressure on the'injection plunger thereafter and the desired degree of setting in the mold, the cam |08 causes contacts When the mold 91 and 98 to be separated, causing breaking of the circuit through coil 85, causing the armature 84'to move rightwardly, causing motor 6| to reverse, causing the valve member in valve 56 to shift upwardly and causing retraction of the injection plunger in order to recharge the heating cylinder.

As soon as the injection plunger 2 starts rearwardly, the unclamping switch |25 which is nor- Vmally closed isopened manually, causing reversal Yof the rotary valve 68, causing shifting of vthe valve member in valve 65 back tothe position shown in Fig. 1, causing the application of liquid pressure in conduit 66 and causing the clamping ram 9 to unclamp the mold halves. The reduc tion in pressure in the line 61 which is now the discharge line for clamping cylinder Il causes the admisssion valve 18 toclose and the nozzle valve 25'to close, the liquid inthe motor 28 discharging through conduit 19 into conduit 61.

When the injection plunger 2 approaches the the discharge Vthe plastic material in the heating cylinder.

fully retracted position, it Vactuatesv the limit switch 89 which is normally open so as' toclose the circuit through the coil 85, causing the rotary valve 60 to be 'reversed',"ausing thev valve member in valve 56 to shift downwardly into the position in Fig. 1, thus causing the hydraulic liquid t'o be applied to the right-hand of piston- 54, causing the injection plunger to reverse and move forwardly, carrying ahead of it th charge of granular plastic which accumulated 'in front of it as itwas retracted. f*

Injection plunger 2 moves forwardly and holds at its forward position under pressure the .circuit remaining as shown. As the cam |08 completed its single revolution, it opened the holding circuitthrough motor |06, causing the timing motor |06 to stop. j Y

The molding cycle is now complete and the machine is in position for another cycle whic is accomplished in the same manner.-

If desired, operation of the unclamping switch being injected after the mold halves have begun toseparate and allowing the iiuent material in the heating cylinder to beheld under the holding pressure exerted on the injection plunger 2 until it is desired to make the next injection. j

If' desired, instead of operating Atheunclamping switch |25 manually, relying on the observation of the operator and necessitating continuous attention throughout the molding cycle, switch |25 may be operated automatically so that it is opened at any desired time from the point Iwhere the injection plunger has caused complete lling of the mold to the point where the injection plunger has resumed its holding pressure' upon For example, switch |25 might be.. opened by the timing cam |08.

Instead of operating the nozzzle vvalve by the pressure in clamping line 61, it may be operated in other ways, such as for example, directly by the movement of the mold halves` together. whereby it, is likewise insured that the valveis not opened except when the mold halves are clamped together to the injection nozzle. the valve 25 might be arranged so that it would be Opened by the forward motion of the injection plunger 2 although this would necessitate a ccmplete change in the molding cycle from that described above because holding pressure would.

not in such case be exerted by the injection plunger 2.

Modification AlSO.'

gio

and moved byarod |3| which: is integral with the valve member |29 and which is i slidably mounted in the bore'|32 in the nozzle' |26.V The rod |3| extendsleftwardly so as to beengaged at its end |33` by the motion rof the mold half |28 towards 'theinjectionnozzle |26. Thus the valve'member is Amoved rightwardly in the space cie'ntly to expose well the ends of the flutes |733,

so that Athe fluent materialv is Vfree to ow into the flutes and into the' mold. Thus, norestriction toow is'ofered at thispointfwith thismodineeformofvaiving, theinjection nozzle is opened atthe instant when 'clamping of the molds to `the -AinjectionI -nozzle occurs and isY closed at the instant when moldhalf |28 -r is pulled away-fromnozzlelZS.'

General Y From the foregoing, it will be-'seen that the present invention provides for the injectionvmolding of thermosetting resins-by heatingthem -to uencyf. while confining them so as to, prevent the liberation of gasV and injecting the material into a mold where free escape of gas isallowed andv where Vheating is carried out to a suicient extent toipernianentlyV set-thematerial. It will be,l understood that the drawingof aV vacuuml upon retraction-of the injection plunger is prevented becausetheheat .causesf eas under pressure to be liberatedgaheadl of.- theinjection plunger and this gas is merely loweredin pressureasthe l injection plunger moves rearwardly. Similarly,

i preferably a't'emperatureof at least 13.0'C. is

as the -inj ceti on .plungermoves forwardly` it merely compresses .this gas andV any entrapped' air andtherefore relief is not necessary. AIt will. iurther beunderstcod that the momentary releasel,I of the pressure of thegases during recharging ofl the injection cylinder is not suiciently prolonged to allow, appreciable setting of the resin. v

The maintenance of the proper temperatures will depend upon theresin or plastic beinginjected; Many of thephenolics becomeuent inr the heating Vchamber at 140 C. andmay be hardcned in theV mold at this'temperature by-sufiiciently prolonged maintenance thereof,- although maintainedinthe heating chamber andat least 150 C. in the mold.` The urea resins set at betweenl30 and 140" C. and may beiheated to atleast C. intheheating chamber and at least 150 C. in the mold although a lower temperature, say C..` may be maintained-in the mold. Under 'some circumstances. the temperature in the heat-ingl cylinder may he as lowas 100 C.,; especially if the material is subjected to very high pressure, say 30.0'30 to 4,0.0Q0 pounds per square inch. during theheating and alsoduring injection. since the. materials dow much more readily. as .thepressureupon them is increased.. lfd-esired, the mainteiance of the desired temperature at a1ccnsiantlevel maybe reflected by -the method of myV cependngapplication, Serial l.

No..309,7j97,filed December' 18. 1939. which disclcses theusc fifa. fused bath at the i'usionpoint around the in jcction cylinder.

sageways il.l The valve member |29 is supported The rotary valves e160 @and It are ofthe shown -my Ycomznding.salpplication ySerial eNo. 167,184- illed` October 4, 1937, andare.-actuatedaby torque :motors sii gandzfi! ffrespectively'l which :are y v 5v injection cylindernhaving fa bore,y van Vinjection adapted 1 to operate ain acontinuous stalled .--service as isa-lso disclosed inssaidfapplication.

AI wish it to .beunderstoodgthat Iintend .to Ainclude as within. myinvention such modiiications as `may bef-necessary -toffadapt -it;to l'varyingcon- .mold hal-vesfio'r opening ksaid injection. passageway tof-ilelese materialrnormaljly retainedunder pressure lmsaidinjectionplunger,

25..;Injection moldingv apparatus comprising y an lpassage,wayslea'dingfrom said bore, .a normally closed valverinsaid passagewayfor opening-and closing the same, an f injectiony plunger slidably mounted 1 in said bore, 'pressuremeans .for norditlons'and'uses and:asffallwithinthe terms/Dr i0 :mally'gplaclng :said plungerrin a forward position spirit of the appended claims.

-Having `thusrfully described my .invention-:what

I claim as new and desireto secure liv-Letters Patentiis:

1.Y Injection. molding apparatus comprising Iaan injection .cylinder-'havinga-'borepfmeans'for heating said- .cylinder,- an injection plunger'reciprocable in said bore.sa-id .plunger being largeriithan and not -slidable :in said lbore under normaltemin said :bore to compress material thereinand normallymaintain pressure thereon,;coop,erating mold halves adapted to `form a mold cavity in communication- `with said fpassagewayf pressure 15 lmeans --for clampinggsaid Amoll halves -together,

Denture,condtionsiandzmeansforgqntrgmng the, Z normalzpositionv upon '.-release of material from diameter of said :plunger to i just "that which is Y slightly smaller-than said -bore:andfslidablegtherein in-.fgas tight, relationship iwhenvsaid `cylinderiis heated comprising -passageways ,in ,said .plunger :said'vborefthroughsaid `open `*valve to l.cause ma- -iterial :to be injected vinto said cavity on lsaid :mutigen-and .time delaygmeans actuated by said :.c-:lampingC pressure. means --for effecting a reciproand means foreircuiaung a .cocling-mediumatcatory charging Stroke ofsaid injection plunger controlled temperature throughsaidjpassageways. 2. Injection molding apparatuszcomprising` an injection cylinder having 'a bore. an injection passageway leadingirom saidbore, valvemeans for opening `and closing-said passageway, meansfgg Vior'heating said injection` cylinder, an'injection plunger in gas tight` but slidablerelationship; in said bore, means ior` normallyfzclosing said valve, meansffor applying pressure-upon saidgplunger :while said: molds Vaie--closed to feed ,materialv into said bore and reestablish the normal pressure vmaintained on the material in the bore.

k6. 'Injection molding apparatus comprisingV an :injection cylinder having a bore, an injection pasrsageway leading fromsaid bore, a 'normally closed :valve in said; passageway. for opening n and closing the same, an injection plunger slidably mounted .infsaidbore',pressure means for normally placwnormauy positionthesameagamst plasticfmayg ing saidplunger in aforward position in said terial 4in, said bore to.;continnously exert: pressure on the material in saidbore, andmeansforcausing yrcciprocation of f said plunger upon completion vof i injection of' material pinto the molds .of the Vinjection molding apparatus to feed plastic material into -said bore andato 1 reestablish: pressure upon the material.

- 3. Injection molding lapparatus comprising an injection vcylinder havingabore, an injection passageway leading Vfrom said: bore, :normally closed 4 valve means constructedand arranged-for opening and closing said passageway, an .injection plunger slidably mounted in 'said-bore and .constructedrand arranged'to prevent escape of gas evolved. 'by material placed within said bore, means for normally positioning said plunger forwardly in saidbore to normally retain pressure on the material in said .borefcooperating'mold halves adapted tofform amold cavityjin communicatlon with said passageway, means for clamping Ysaidmold halvestogether under pressure, and -meansvactuating said valve means'to opensaid passageway when said mold halves` are clamped under pressure, said opening of said valve permitting said plunger to move.forward.under ,0 pressure normally retainedthereon to causev material to be ejected from said bore into said mold .bore to-compress. material thereinand normally maintain pressure thereon, cooperating mold halves adapted toi-.form 'a mold cavity in communication with said passageway, pressure means 40 for vclamping said moldhalves together, means l actuated by said pressureclamping means im- ;mediately uponl development of `clamping pressure for .opening said valve, means for releasing pressure on. the mold halves-for unclamping said 5 mold halves,.fand actuating means released. by release of Vclamping pressure `for immediately closing saidv valve to prevent. material being forcedthrough said passageway. by the pressure normally maintained #on .the material by said 50 plunger.

7. njectlonimolding apparatus comprising an Ainjection Vcylinder. having a bore, an injection passageway leading from said bore, a normally closed valve in-saidpassageway-for opening and 5 closing the sanie,.an injection-plunger slidably mountedfin said borepressure means for norin said-'bore to vcompress material therein and normally maintain pressure thereon, cooperating mold halves adapted to form a moldfcavity in communication with said passageway, pressure Y means for clampingV said mold rhalves together, vmeans actuated by said pressure clamping` means immediately upon; development of clamping pres- 65 sure for` opening said-ivalve,.said.plunger pressure means moving said. plungerforward of its normal position upon release of material from'said bore `through said open valveto .cause material to beinjected into said cavityby the pressure-nor- 70.mally maintained on vsaid plunger, vtime delay means'initiated yby said clamping means for retracting said in jectionplunger after a predetermined time intervalafter clamping has been effected,` and means operated by said injection llafplunger as it approaches its retracted position galassi.

or stopping said retraction and causing an mforward movement of said plunger under of ,id pressure means for said j' ,o ,l en the plunger forwardly in said bore an reestablish pressure on the material in said bore.

8. injection molding apparatus comprising an ndwtion cylinder 'saving a bore, an injection passageway leading from said bore, a normally closed valve in said passageway for opening and elosin the same, an injectionplunger slidably mounted in said bore, pressure .means for no1'- mally placing said plunger in a forward position in said bore to compress material therein and normally maintain pressure thereon, cooperating meid halves adapted to form a mold cavity in communication with said passageway, pressure means for clamping said mold halves together.,

:means actuated by said pressure clamping means immediately upon development of clamping pres= sure for opening said valve, said plunger pressure means moving said plunger forward of its y normal position upon release of material from said bore through said open valve to cause material to be injected into said cavity bythe pres sure normally maintained on said. plunger, time delay means initiated by said clamping means for retracting said injection plunger a predetermined time interval after`c1amping has been ef fected, means for actuating said pressure clamping means to initiate unclamping of said molds, means responsive to a release of clamping pressure to close said valve, and means operated by said ineotion plunger 'as it approaches its re tracted position for stopping said retraction and causing an immediate forward movement of said plunger by said plunger pressure means to rec position the plunger forwardly in said bore to res estabiish pressure on the material in said bore,

' said mold clamping release and closure of said valve being eected while said injection plunger 2o is traversing its reoiprocatory stroke. 

